1. Field of the Invention
The invention relates in general to a scanning apparatus, and more particularly, to a method of removing memory of a scanning apparatus.
2. Related Art of the Invention
A scanning apparatus is a machine between a copy machine and a camera. In the past, a scanning apparatus was so expensive that only art related workers could use it. Recently, the development of computer technology and market competition has caused the price of the scanning apparatus to drop drastically. A scanning apparatus has thus become one of the major peripherals of a personal computer.
A scanning apparatus can be categorized into various forms according to price or function. For example, a scanning apparatus includes the palm scanner, the paper feeding scanner, the card scanner, the film scanner and the flatbed scanner. Among various types of scanners, the flatbed scanner includes a glass flatbed to dispose a document or a picture thereon. A sensor then moves to read the data of the document or the picture. As the structure of the flatbed scanner is not very complex, and the operation is user friendly, the flatbed scanner is currently the most popular type of scanner.
In the currently available scanning apparatus, a memory buffer, for example, a dynamic random access memory (DRAM) is used to temporarily store the data extracted by the image extraction device such as a charge-coupled device (CCD). The computer then reads and processes the data stored in the memory buffer. FIG. 1 shows a schematic block diagram of using a conventional scanner 10 to transmit the data extracted by an image extraction device 12 and stored in a memory buffer 14 to a computer 16. In FIG. 1, to transmit the data extracted by the image extraction device 12 of the scanner 10, the image extraction device 12 temporarily stores the data in the memory buffer 14 of the scanner 10 first. When the computer 16 is ready for processing data, the data stored in the memory buffer 14 is then read by the computer 16. The data transmission between the image extraction device 12 and the computer 16 is described as follows. FIG. 2 is a sequence diagram of a Transfer signal TR and a shift signal PH during the exposure time. As shown in FIG. 2, when the Transfer signal TR is enabled (at a high level), the image extraction device 12 transmits each pixel of the data of one scan line to the computer 16 via the shift signal PH during the period of one Transfer signal TR (the exposure time). Meanwhile, the shift signal PH is enabled at a high level, and the shift signal PH shifts one pixel of the data of the scan line during one period thereof. The period of the shift signal PH is constant. If the period, of the shift signal PH is 1 ms and the scan line has 5400 pixels per inch, the image extraction device 12 will transmit the data of the scan line to the computer 16 within 5400 ms (the exposure time). If the computer fails to read the data of the scan line within the exposure time, a data reading error is caused. Therefore, the memory buffer 14 is used to temporarily store the data of the scan line transmitted via the shift signal PH, providing sufficient time for the computer 16 to read the data of the scan line. As the conventional scanner 10 requires the memory buffer 14 to ensure the correct data transmission between the image extraction device 12 and the computer 16, the cost is increased.